Victorian Premier Daniel Andrews (Image: AAP /David Crosling)

How many known close contacts of COVID-19 carriers in Victoria and NSW are notified by government tracing teams?

The answer may seem self-evident — all of them — but if the experience of other countries is anything to go by, many close contacts may be falling through the gaps of the tracing system.

In England, a quarter of people referred to National Health Service (NHS) tracers cannot be reached due to a combination of unanswered calls and incorrect contact details. Of referrals who are successfully interviewed, around a third of the close contacts they provide to tracers are also proving impossible to find.

Putting both factors together means tracing teams in England are currently reaching only around half of the close contacts of known coronavirus carriers. Half.

Worryingly, the US makes England’s numbers look good. In New York, as few as 35% of people referred to tracing teams have been willing or able to provide a list of close contacts. Some areas of New York have even resorted to issuing subpoenas to force suspected coronavirus spreaders to cooperate. No wonder White House health adviser Dr Anthony Fauci has admitted US contact tracing is “not going well”.

So is the contact tracing hit-rate any better in Victoria and NSW? It seems an important thing to know — but we don’t.

Australia’s lack of data

Unlike their counterparts in England and the US, neither the Victorian Department of Health and Human Services nor the NSW Ministry of Health publishes performance data about their contact tracing efforts. Both have refused to provide figures to Crikey.

According to Professor Catherine Bennett, chair in epidemiology at Deakin University, Australia’s contact tracing performance is likely to be a lot better than in England and the US. But, she says, “a relatively small percentage” of contacts may still be unreachable.

“We have been nowhere near as overwhelmed by case numbers as the UK, so I think that alone means we have probably had more capacity to be more persistent in our detective work following up cases and contacts,” Bennett tells Crikey.

The maths suggests a small percentage of missed contacts is still a problem. Even if just 3% of close contacts prove to be unreachable — a mere 10th of the contact failure rates in England — that still equates to hundreds of close contacts in Victoria and NSW never being informed of their status. A 10% contact failure rate would put the number of missed close contacts into the thousands.

(Bennett also points out that less than 1% of tests are positive, including close contacts, so missing a few hundred might only mean a couple of them actually have the disease.)

We can only hope Australia is performing better than England and the US, but without seeing official figures it is impossible to know.

Why is contact tracing so tricky?

Bennett says outright non-compliance with contact tracers is rare, but getting useful information from people requires a lot of time and skill.

“I’ve had contact tracing calls with hundreds of people over a variety of [non-COVID] outbreaks, and don’t recall anyone flat-out refusing,” Bennett says. “They always gave a little info at least, but it can take a lot of time to work with them to even get that.”

“The ability of the contact tracers to build rapport, trust and confidence at first contact is really important and why so much effort needs to be put into training — even in this current crisis.”

Perhaps the biggest obstacle for tracers is getting people to answer their phones in an era when few people are willing to field calls from unknown numbers.

In the US state of Massachusetts, health officials have responded to low response rates by launching an initiative called “Just answer the call”. Instead of an anonymous number on the screen, their contact tracers are also now identified with a caller ID showing they are part of the “MA COVID Team”.

Similarly, New York City has taken out social media ads saying: “HIT ACCEPT. NYC IS CALLING!”.

Victorian Premier Daniel Andrews has conceded “there will always be instances where despite multiple phone calls you can’t actually connect with the person, despite every best effort”. But, for now, at least, official contact tracing performance figures remain under wraps. 

Releasing the data would not immediately solve the difficulties of contact tracing. But it would at least shine a light on the size of the challenge — and perhaps encourage more people to pick up the phone when the tracing team calls.